AT&T just doesn’t seem to be able to keep it nose clean when it comes to its “old” unlimited data plans. While AT&T has done a pretty amazing job of shifting the majority of its smartphone customers over to more lucrative (for AT&T) Mobile Share Value plans, it still has to contend with unlimited data customers that it feels are abusing the service. However, the company has handled the matter in a somewhat shady fashion for the past four years.

Needless to say, the FCC isn’t too happy about the games that AT&T has played in the past, and has fined the company $100 million for misleading customers. The FCC contends that AT&T wasn’t completely transparent when it came to disclosing the diminished data speeds to customers. The FCC states that it not only received thousands of complaints over the years from AT&T customers lamenting reduced data speeds, but it also discovered customers had to put up with throttled data speeds for on average 12 days during a typical month-long billing cycle.

“Consumers deserve to get what they pay for,” said FCC Chairman Tom Wheeler. “Broadband providers must be upfront and transparent about the services they provide. The FCC will not stand idly by while consumers are deceived by misleading marketing materials and insufficient disclosure.”

Back in early May, AT&T decided to go easy on its customers that were still rockin’ grandfathered unlimited data plans. AT&T adjusted the language in its policy to indicate that it would no longer implement blanket data speed throttling for customers that used more than 5GB of data during a given billing cycle. Instead, it would throttle customers only if they were connected to a heavily congested cell tower and would take off the speed limiter once congestion on the connected tower diminished or if the user connected to a less saturated tower.

While this was definitely a sigh of relief for customers that don’t want to give up their unlimited data plans, it’s still not ideal. After all, AT&T doesn’t have such data speed restrictions for customers on its Mobile Share Value plans even though it offers data allotments of up to 50GB, whereas unlimited customers can face a potential speed cut after just 5GB of usage depending on “tower conditions.”